1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device and, more specifically, to a manufacturing method of a semiconductor device including an impurity region used for an interconnection structure.
2. Description of the Background Art
A formation method of an impurity region of an interconnection structure applied to common DRAM (Dynamic Random Access Memory) will now be described referring to FIGS. 12-14.
Referring to FIG. 12, an element isolation region 12 is provided in a surface of a semiconductor layer (including semiconductor substrate) 10 to define an active region. An n-type impurity region 21 and a p-type impurity region 22 doped with impurities are provided in this active region. On the surface of semiconductor layer 10, a silicon insulating layer 11 provided with a contact hole 51a connecting to n-type impurity region 21 and a contact hole 52a connecting to p-type impurity region 22 is provided.
A contact plug 51 electrically connected to n-type impurity region 21 is provided within contact hole 51a, and a contact plug 52 electrically connected to p-type impurity region 22 is provided within contact hole 52a. An n+ type impurity region 21a for decreasing a contact resistance with contact plug 51 is formed within n-type impurity region 21, and a p+ type impurity region 22a for decreasing a contact resistance with contact plug 52 is formed within p-type impurity region 22.
A manufacturing method of a semiconductor device having the above-described structure will briefly be described. Referring to FIG. 13, element isolation region 12 is formed in a prescribed region of the surface of semiconductor layer 10. Thereafter, n-type impurity region 21 and p-type impurity region 22 are formed in the active region of semiconductor layer 10 by impurity implantation.
Silicon insulating layer 11 is then formed on the surface of semiconductor layer 10. Contact holes 51a, 52a respectively connecting to n-type impurity region 21 and p-type impurity region 22 are formed in silicon insulating layer 11 using a dry etching method such as a RIE (Reactive Ion Etching) method using a photoresist film on silicon insulating layer 11 having a prescribed opening pattern as a mask using a photolithography technique.
Contact hole 51a is then covered with a resist film 14, and a p-type impurity such as B or BF2 is implanted into the surface of semiconductor layer 10 through contact hole 52a to form p+ type impurity region 22a. 
Referring to FIG. 14, after removing resist film 14, contact hole 52a is covered with a new resist film 14, and an n-type impurity such as P or As is implanted into the surface of semiconductor layer 10 through contact hole 51a to form n+ type impurity region 21a. 
Thereafter, contact plugs 51, 52, which are made of polysilicon or the like and are electrically connected to n+ type impurity region 21a and p+ type impurity region 22a respectively, are formed by filling contact holes 51a, 52a. 
The aforementioned element isolation region 12 is an isolation region formed by a method such as an embedding method of a thermal oxide film or an oxide film. In addition, silicon insulating layer 11 is an insulator film such as a TEOS (Tetra Etyle Ortho Silicate) oxide film or a nitride film, or a film formed by superimposing these films, which is deposited using a low-pressure or normal-pressure CVD (Chemical Vapor Deposition) method, and has a thickness of about 50 nm-1000 nm.
In the above-described manufacturing method, the impurity region is formed for decreasing the contact resistance using the contact hole. For forming n+ type impurity region 21a and p+ type impurity region 22a having different conductivity types, however, covering processing using the photolithography technique to cover the other contact hole with a resist film is necessary in each impurity implantation step to semiconductor layer 10. This increases manufacturing steps and manufacturing cost of the semiconductor device.
The present invention was made to solve the above-described problem. An object of the present invention is to provide a manufacturing method of a semiconductor device which does not need covering processing using a photolithography technique when impurity regions of different conductivity types are formed using contact holes.
In a manufacturing method of a semiconductor device according to the present invention, a first conductivity type impurity region and a second conductivity type impurity region are included in a semiconductor layer. The method includes the steps of: forming on the semiconductor layer an insulating layer including a first contact hole having a top-end opening shape exposing a surface of the semiconductor layer for an implantation angle of an impurity to a normal of the semiconductor layer and a second contact hole having a top-end opening shape blocking a surface of the semiconductor layer for the implantation angle; implanting an impurity of a first conductivity type into the semiconductor layer with the implantation angle using the insulating layer as a mask to form the first conductivity type impurity region only in a surface portion of the semiconductor layer exposed by the first contact hole; and forming the second conductivity type impurity region only in a surface portion of the semiconductor layer exposed by the second contact hole using the second contact hole of the insulating layer.
According to the above-described manufacturing method of a semiconductor device, when forming first and second impurity regions of different conductivity types using contact holes having different opening shapes, one impurity can be implanted at the first contact hole because the surface portion of the semiconductor layer is exposed for the implantation angle of the impurity to a normal of the semiconductor layer, while the impurity is not implanted at the other contact hole because the surface portion of the semiconductor layer is blocked.
As a result, it is unnecessary to form a conventionally required photoresist to prevent an impurity from being implanted into other regions when the impurity is implanted into a prescribed region. Therefore, manufacturing steps of the semiconductor device can become more simple, and the manufacturing cost can be reduced.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.